1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device.
2. Description of Related Art
Along with progress in the miniaturization of semiconductor devices, the width of an interconnect for connecting between elements has also been reduced. If the electrical resistance of the interconnect increases due to a reduction in the width thereof, it is difficult to perform predetermined circuit operation. Although a rise in interconnect resistance can be suppressed by increasing the thickness of a conductive film used as the interconnect, in that case, such problems as described below are involved:
In order to precisely process miniaturized interconnects, etching using a hard mask is practiced in general. As the thickness of a conductive film for interconnects is increased, a hard mask also needs to be thick-filmed, in order to ensure resistance to etching. Accordingly, it has become difficult to precisely process the hard mask itself. In addition, an increase in the post-etching aspect ratio of interconnects, including hard mask portions provided thereon, has led to the occurrence of a phenomenon that an interconnect layer collapses during a manufacturing process. This has been a cause for a decline in production yields.
As a method of processing a thick-filmed interconnect layer without using a hard mask, there is known a damascene method in which trenches corresponding to an interconnect pattern are formed in an interlayer insulating film, and a conductive film is filled in the trenches. For example, JP2000-091340A describes a method of forming damascene interconnects in an interlayer insulating film on a semiconductor substrate by performing chemical-mechanical polishing using a polishing stopper film.
On the other hand, there is known a self-alignment method (SAC method) as a technique to densely dispose interconnects. According to the self-alignment method, it is possible to easily form a hole adjacent to an interconnect by covering upper and side surfaces of the interconnect with an etching protection insulating film and performing dry etching for the purpose of forming holes for plugs in an interlayer insulating film, as described in, for example, JP2002-319551A.